Conventionally, a combined heat exchanger configured to enable heat exchange among three types of fluids has been known. For example, a heat exchanger disclosed in Patent Document 1 is a combined heat exchanger configured to enable both heat exchange between a refrigerant of a refrigeration cycle device and a vehicle exterior air (outside air) and heat exchange between the refrigerant and a coolant that cools an engine.
Specifically, the heat exchanger of this Patent Document 1 is configured such that multiple linear refrigerant tubes each having both ends connected to refrigerant tanks that collect and distribute refrigerant is stacked, a heat pipe having one end connected to a coolant tank through which a coolant flows is arranged in parallel to the refrigerant tubes between the respective stacked refrigerant tubes, and fins for promotion of heat exchange are arranged in outside air passages formed between the refrigerant tubes and the heat pipe.
In the refrigeration cycle device of Patent Document 1, when the combined heat exchanger is permitted to function as an evaporator that allows the refrigerant to absorb a heat of an outside air and a heat (that is, waste heat of the engine) of the coolant to evaporate the refrigerant, frost formation of the heat exchanger is suppressed by the heat waste of the engine which is transmitted from the heat pipe.